Best Chimney Insulation???

[papossefan]

I have a masonry chimney with a terracotta liner which has had a stainless liner installed inside the terra cotta. I need to insulate between the old terracotta liner and the new stainless liner. I have been looking at loose vermicuite and a product called thermix which is mixed with water and poured down the chimney. My question is which one is better? I am kinda leaning toward the thermix because I have used vermiculite in the past but with mixed results. I was just wondering what everyone's opinion is and if their are any other products out there that I haven't heard about that I may be able to use.

 

[dave_dj1]

May I ask why it has to be insulated?
thanks,
dave

 

[brenndatomu]

I thought about doing pour down too. Ended up going with wrap since it was a new liner install.
The thing about the thermix type product that I didn't like was that it makes the liner permanent. Thermix does add some structure to your chimney though if that's something you need.
FWIW, if I needed to insulate an existing liner, I'd lean toward the vermiculite.

 

[us2bnuts]

I have a plain steel liner installed just like yours. I simply put fiberglass batt insulation at the top and bottom. I know that I will need to replace the steel pipe at a later date and I can simply pull the insulation out of the way. No problems in the last 3 years so far.

 

[Old Doug]

I went with vermiculite. It was no fun careing it up the ladder to the roof and then up another ladder to the chimney. But it gave my neighbors some thing to watch.What problems did you have with the vemiculite?

 

[Hddnis]

I've used Perlite with good success on a few liner installs. If you ever need to work on the liner the perlite can be vacuumed out easily.



Mr. HE

 

[woodchuck357]

Shop vac set up to blow with a venturi suction can be used to move

vermiculite from the ground into the chimney with out making lots of trips and a mess in the neighborhood. Sifted wood ashes used to be used as non flammable insulation.

 

[deranged]

I used vermiculite in mine, total cost to do my 25 foot chimney was 39 bucks. 13 bucks a bag at Menards.

 

[*ryan]

I have a plain steel liner installed just like yours. I simply put fiberglass batt insulation at the top and bottom. I know that I will need to replace the steel pipe at a later date and I can simply pull the insulation out of the way. No problems in the last 3 years so far.

i did the same exact thing
no problems
mine has been in probably about 3 years aswell

the woodstove is my source of heat, the electric baseboard heat is not turned on

so it runs 24/7 and have had no issues with the insulation just on top and bottom

 

[taskswap]

Any of these products will insulate well. The only thing that makes Thermix (or any of its competitors special) is the addition of some Portland Cement, which you could do yourself (anywhere from 6:1 to 10:1 BY VOLUME, I believe). You wet it slightly (not like concrete) and pour it down just like the rest.

The advantage of this is it holds the liner centered in the chimney, giving it a little rigidity. It also keeps most of the water out - vermiculite and perlite straight can absorb a lot of rain if there's a leak in the top cap somewhere. Neither of these things is harmful, but they do reduce the insulating value.

If you want to take it out you still can. It's pretty weak - you can shake it about to break it up and then vacuum it out just like raw Perlite/Vermiculite.

It's hard work moving the stuff around. I tried all sorts of tricks. Best thing for me was a plastic recycling bin with some tape over the bottom holes. YOu can mix and pour right from there, and the size is about right for the weight I'd want to be carrying around a roof.

 

[Old Doug]

I would like to know if insulation is a realy needed. I know guys that get along with out it.

 

[Bowwow122]

I mixed my own..5 gallon bucket of cement, 1 bag vermiculite, 4-6 gallons water. I also made some spacers
from wire wrapped around a dowel then hose clamped on every 4 feet or so. It holds the liner nice and tight
for brushing.

 

[steved]

When my folks had their masonry chimney lined with stainless, the contractor pour loose/dry vermiculite in the void...there are two issues:

1) the vermiculite settles, and

2) if you ever get a loose connector or penetration through the concrete; the vermiculite will literally run out onto the floor.

I would not use vermiculite alone, I would use the portland/vermiculite mix...

 

[Hddnis]

I would like to know if insulation is a realy needed. I know guys that get along with out it.

Insulation will keep more of the heat in the pipe. Properly set up it means you will run a cleaner chimney and get more heat out of the wood you burn. There are many liners that just run up the flue and work that way for years, but at a reduced efficency and greater risk of fire. The insulation reduces heat cycling in the masonry making it last longer. If you have a fire in the liner with proper insulation around it there is little chance it will get the masonry hot enough to fail, which reduces the chance the chimney fire will spread to the rest of the structure. While all of the benefits of insulation around a liner are well proven as you mentioned there are still plenty who get by without it. Best thing is to do a little research so you can make an informed decision. I would personally never use a liner without insulation after having a chimney set up that way and then upgrading it after a year to a liner insulated with perlite. Night and day difference on the same stove, much better draft and cleaner chimney with the insulated liner.




Mr. HE

 

[Old Doug]

That makes scents. I may have to pull my liner and saveing and replaceing the verniculite is not something to look forward to.